NotStringtype

{
	toUpperCase?: never;
	toLowerCase?: never;
}

Property	Type
`.toUpperCase`	`never`
`.toLowerCase`	`never`

Type that never matches the string type.

string itself is iterable (iterating over its individual characters) and implements Iterable<string>
Using Iterable<string> & NotString allows an iterable containing strings but not string itself.
This helps catch this category of subtle errors.